The use of optical fibers in telecommunications applications requires the ability to switch an optical signal between optical fibers with low loss over a varying number of switch cycles. The optical fibers may be either monomode or multimode fibers. Monomode fibers have a light transmitting core approximately one-tenth the diameter of multimode fibers. Monomode fibers, however, exhibit lower signal losses per unit distance than multimode fibers and are, therefore, more desirable in long-haul optical transmission systems. The number of switching cycles for either type of optical fiber can vary from one or two to several thousand in the switch service life. A high degree of reliability is particularly important in many applications, such as undersea fiber transmission systems, where the optical switch is not readily repaired or replaced.
The switching function in optical fiber switches is typically accomplished through the use of an optical device and/or fiber movement. In switches utilizing an optical device, such as a lens or mirror, the optical signal is directed by the optical device between spatially separated optical fibers. Such switches typically provide satisfactory reliability but exhibit undesirable signal losses and crosstalk levels due to the optical device and the inherent separation between optical fibers. In moving fiber switches, switching is accomplished by the displacement and precise alignment of one fiber relative to another. A number of moving fiber switch designs exist which can achieve low signal losses and crosstalk levels. See, for example, U.S. Pat. No. 4,033,669 to Hanson, issued July 5, 1977 and U.S. Pat. No. 4,220,396 to Antell, issued Sept. 2, 1980. The problem with moving fiber switches, however, is that the signal loss and crosstalk level tend to increase significantly after many switch operations. Moreover, most designs are not readily adaptable for use with either multimode or monomode optical fibers.
In light of the foregoing, a moving fiber switch for either monomode or multimode fibers that exhibits low-loss over thousands of switching cycles would be extremely desirable.